Tamiya Red Bull RB6

"Cheap" depends on where you live.  Revell kits cost 50 to 60 US$ here in Japan - as much as larger 1/20 kits from other makers, with twice as many parts, and twice as much detail.  I understand they're cheap in Europe, though.

Chris

I have a 1/8 Ferrari F1 car that was released about 5 years ago - gathering dust on the top shelf - may have instructions somewhere

Didn't Lego have a Ferrari F1 car a few years ago?

Revell make the cheapest and most basic f1 models, probably best for a ten year old. Some of them can be found for as little as a tenner these days.